Suzuki: Engine K6A-YH6. Manual - part 7

THEORY OF OPERATION

4-5

4

4.3 Cooling System

See Figure 4-3.

Figure 4-3

The cooling system includes the radiator (4), water pump 
(5), thermostat (7), and engine coolant passages.

Coolant is circulated from the water pump (5) into the 
engine coolant passages and circulates around the 
cylinders. From the cylinders, coolant flows up through 
the block deck passages and into the cylinder head (2). 
In the cylinder head (2), the coolant flows through 
passages around the intake and exhaust ports, valve 
seats, and combustion chambers. Coolant flows toward 
the rear of the cylinder head (2) and exits through the 
thermostat housing (8).

During the warm-up period, the thermostat (7) is closed 
and coolant flows only through the jiggle pin (1) opening 
to provide a fast warm-up period. The jiggle pin (1) also 
helps ensure that no air is trapped in the engine when 
filling the cooling system.

Once the engine has reached operating temperature, the 
thermostat (7) opens and allows coolant to flow through 
the upper radiator hose to the radiator (4) top tank.

Coolant circulates through the radiator (4), dissipates 
heat, and then flows out of the radiator (4) through the 
lower hose and into the suction side of the water pump 
(5).

If coolant temperature begins to become excessive, the 
radiator pressure cap will open and allow excess coolant 
to flow into the overflow bottle (3). When coolant 
temperature lowers enough, the radiator cap will close. 
As the coolant continues to cool, a vacuum will be 
created in the radiator (4). This will open a valve in the 
radiator cap that will syphon the excess coolant from the 
overflow bottle (3) back into the radiator (4). 

Coolant continues flowing through the engine and 
radiator circuit until the coolant temperature drops below 
the thermostat (7) opening temperature. The thermostat 
(7) will remain open until coolant temperature falls below 
the thermostat closing temperature. At that time the 
thermostat (7) will close and begin a new cycle of 
warming the coolant. 

This repeated cycle of temperature control keeps the 
engine at the optimal temperature for clean and efficient 
performance.

1

Jiggle Pin

5

Water Pump

2

Cylinder Head

6

Cylinder Block

3

Overflow  Bottle

7

Thermostat

4

Radiator

8

Thermostat Housing

4

5

6

7

8

1

3

2

4-6

THEORY OF OPERATION

4

Thermostat

See Figure 4-4.

Figure 4-4

The cooling system thermostat (1) is contained in the 
thermostat housing located on the rear of the cylinder 
head. The thermostat controls the flow of coolant through 
the engine. The thermostat is in the closed position when 
the engine is cold. When coolant temperature reaches 
190° F (88° C) the thermostat begins to open, allowing 
coolant to circulate. The thermostat opens fully when 
coolant temperature reaches 205° F (96° C), allowing full 
coolant system circulation. As engine load is varied, the 
thermostat will vary its open or closed percentage to 
maintain the engine in an optimum temperature range. A 
jiggle pin is provided in the thermostat to aid in the 
bleeding of the system when filling. 

Water Pump

See Figure 4-5.

Figure 4-5

The engine is equipped with a belt-driven water pump (1) 
driven from the crankshaft pulley. The water pump 
circulates coolant throughout the entire cooling system. 
The water pump is equipped with a “weep hole” for 
indication of seal wear. The pump is serviceable as a unit 
only.

TN0573

1

TN0747

1

THEORY OF OPERATION

4-7

4

4.4 Front Cover, Timing Chain, 
and Tensioner

See Figure 4-6.

Figure 4-6

Attached to the front of the engine is the one-piece cast 
aluminum front cover. The front cover attaches the oil 
pump pickup strainer and houses the oil pump and front 
seal. Contained under the front cover is the timing chain, 
chain guide, and chain tensioner setup.

1

Crankshaft Pulley

6

Tension Adjuster

2

Front Cover

7

Chain Guide

3

Tensioner Link

8

Crankshaft Sprocket

4

Tensioner

9

Oil  Pump

5

Timing Chain

10

Pickup Strainer

TN0748

1

2

3

4

5

6

7

8

9

10

4-8

THEORY OF OPERATION

4

Front Cover

See Figure 4-7.

Figure 4-7

The front cover (1) houses the crankshaft-driven oil pump 
(2) and front seal (3). Attached to the bottom of the cover 
is the pickup strainer (4) for the oil pump.

Timing Chain

See Figure 4-8.

Figure 4-8

For the camshaft drive, a highly durable chain drive 
system is used.

Through the timing chain (1), the crankshaft rotation is 
transmitted from the crankshaft timing sprocket (7) to the 
camshaft timing sprockets (2 and 5) installed on the end 
of the intake and exhaust camshafts.

The timing chain has aligning links (3, 4, and 8) that are 
used for aligning with the timing marks on the respective 
camshaft sprockets and crankshaft sprocket.

A chain guide (6) and chain tensioner (9) system are 
used to ensure quiet and accurate operation.

Tension Adjuster

See Figure 4-9.

Figure 4-9

The tension adjuster (6) has a plunger (4) inside, which 
pushes against the tensioner link to give proper tension. 
This plunger is operated by engine oil pressure (1) as 
well as spring tension (3). The plunger is designed to 
travel in only one way. Once the plunger has moved 
outward, it will not come back due to the function of the 
ratcheting mechanism (5).

There is a check ball (2) inside the plunger (4), which 
keeps hydraulic pressure from dropping. With this 
provision, the plunger can resist and absorb a kickback 
force. During operation under low oil pressure, the ratchet 
keeps the plunger from being pushed back, allowing 
tension of the chain to be maintained. The result is quiet 
operation without chain flapping.

TN0749

1

4

2

3

TN0502

1

2

3

4

5

6

7

8

9

TN0503

1

2

3

4

5

6